6.8 V10 E450 mpg on Ford

Camper 2012 wrote:
some people say 7.5 some people say 10 now I'm confused

It depends on how one drives. Above 30-35 mph most of the drag is from pushing air, that goes up with the square of speed, the amount of power needed and fuel used thus goes up with the cube of speed.

The range of MPGs observed can be even greater than that. I'll say 5 MPG to 12 MPG to confuse you more.

My 2003 E-450 carrying 30-foot 8 1/2 x 11 1/2 house, usually loaded to about 13,000 pounds has average 8.2 MPG over 30,000 miles. I've recorded every mile, every gallon. Individual fills have ranged from 4.9 to 12.1 MPG, depending mostly on how fast I've been driving, whether I have headwinds or tailwinds, or if I'm climbing over mountain passes. Traveling mostly on the plains where wind speeds are often 15-30 mph, whether I'm fighting that wind or it is pushing me makes a huge difference. Also, climbing a 6% grade at 50-60 MPH will at least trip fuel consumption, compared to running on the flats at that speed.

In Missouri, on the Interstates, I'm going guess about 8 MPG. Most drivers in this part of the country have difficulty staying under the speed limit, he likely won't be cruising 55 MPH in 70 MPH zones. I-44 and south, you've got a lot of grades going across valleys in the Ozark Plateau, and going downhill you don't really get back all the extra gas you used trying to maintain highway speeds going up the hill.